Electrooptical tube



Patented Nov. 13, 1934 UNITED STATES ELECTROOPTICAL TUBE Frank Gray, NewYork, N. Y., assignor to Bell Telephone Laboratories, Incorporated, NewYork, N. Y., a corporation of New York Application March 20, 1930,Serial No. 437,331

2 Claim.

This invention relates to electro-optical tubes and more particularly tophotoelectric tubes.

An object of the invention is to provide an improved photoelectric tube.

In an example of practice illustrative of the invention a closed vesselcontaining an inert gas such as argon at low pressure is provided withtwo main electrodes to which is connected an alternatng current sourceof power. Adjacent to the discharge path between the main electrodesthere is a light sensitive electrode adapted to emit photoelectrons intothe main path when illuminated and thus initiate the main discharge.

In this system only a very small current flows to l the light sensitiveelectrode which is protected against injury from the main discharge. Anysuitable work circuit may be energized by the discharge current.

The invention will now be described more in detail having reference tothe accompanying drawing.

Fig. 1 shows one embodiment of the invention.

Figs. 2 to 5 show modified forms of the photoelectric device of Fig. 1.

Identical elements are designated by the same reference characters inthe several figures.

Referring now to Fig. 1, a gas-tight vessel 5. preferably of glass hasmounted therein a ring shaped anode 6, a cup shaped electrode 1 and alight sensitive cathode 8. Terminal wires- 9, 10 and 11, are providedfor the elements 6, 7 and 8 respectively. The bottom of the cup 'I isprovided with an aperture so that the cathode 8 may be illuminated bylight (represented by the dashed lines and arrows) shining through thering anode 6 and the aperture in the cup shaped electrode 7. The vessel5 contains an inert gas such argon at low pressure.

Alternating current potential from an alternating current source 12 isimpressed through transformer 13 and condenser 14 upon the mainelectrodes 6 and 7 through terminal wires 9 and 10. A steady biasingvoltage is also impressed thereon from battery 15. A steady voltage isalso impressed upon the electrode '7' and cathode 8 from battery 16through resistance 17.

The emission of electrons from cathode 8 for a given voltage impressedthereon is dependent upon the illumination thereof. The sparking voltageof the gas between the anode 6 and the electrode 7 is lowered by theemission of electrons from the light sensitive cathode 8. The voltagesin Fig. .1 may therefore be adjusted so that with a given illuminationof cathode 8 insufficient electrons are emitted to produce a dischargebetween the anode 6 and the electrode 7 while an increase inillumination will initiate such a discharge which will continue untilthe voltage between the anode 6 and the electrode 7 is suiiicientlyreduced. Such reduction in the present arrangement is accomplished oncefor each cycle oi. the alternating current voltage from source 12. Thisoccurs when the alternating current voltage opposes the steady voltagefrom the battery 15.

In the arrangement of Fig. 1 large discharges between the anode 6 andthe electrode 7 may take place without injuring the light sensitivecathode 8 which is protected by being located within the cup shapedelectrode 7. Any suitable work circuit may be energized by the dischargecurrent between the anode 6 and the electrode '7. In Fig. 1 such acircuit is indicated by the circle M.

In the modification of Fig. 2 the cup shaped electrode 18 is formed of ametallic wire mesh through which the light shines to illuminate thelight sensitive cathode 8.

In the arrangement of Fig. 3, the ring shaped anode 6 is replaced by ametallic wire 19. The cup shaped electrode 7 is replaced by theelectrode 20 in the form of a flat plate with an aperture therethrough,the light sensitive cathode 8 being in the form of a plate placed behindthe electrode 20 on the side opposite the anode'19.

' In Fig. 4 a metallic wire screen 21 is used in place of the electrode7- and the light sensitive cathode corresponding to cathode 8 consistsof a coating 22 of light sensitive material deposited on the insidesurface of the enclosing vessel 5.

The modification of Fig. 5 is similar to that of Fig. 3 except that theelectrode 20 is replaced by a metallic wire screen 23.

In each of these modifications the light sensitive cathode is protectedfrom injury by the main discharge between the anode and the otherelectrode.

Obviously there are other modifications which come within the purview ofthis invention, the scope of which is defined by the appended claims.

What is claimed is:

1. An electro-optical tube comprising a closed vessel, a cup shapedelectrode having an aperture in the bottom, a ring shaped electrodeoutside said cup but adjacent to the bottom of said cup, and a lightsensitive electrode within said cup.

2. An electro-optical tube comprising a closed vessel, an opaquecup-shaped electrode having a light transmitting aperture in the bottom,a second electrode outside said cup but adjacent to the bottom of saidcup, and a light sensitve electrode within said cup.

FRANK GRAY.

